This is a renewal of a Program Project on the Molecular Basis of Biological Structure and Recognition. As before, the main goal of the Program Project is to bring together and strengthen the collaboration among four structural molecular biologists, in order to study problems in the structure, recognition and interactions of biological macromolecules and complexes. Physical techniques used include x-ray crystallography and two-dimensional nuclear magnetic resonance studies of nucleic acids and proteins, and computational biochemistry. Specific goals to be pursued include: (1) X-ray and NMR examination of synthetic DNA oligomers, and their complexes with antitumor drugs and proteins, the latter including the fis enhancer-binding protein of Salmonella and the TFIID TATA-binding protein of yeast [Dickerson, Feigon]. (2) Design of more efficient sequence-specific DNA-binding antitumor drugs, as vectors capable of differentiating between neoplastic and normal cells, or between invader and host cells [Dickerson] (3) Crystal structure analyses of the multi-subunit allosteric enzymes glutamine synthetase and ribulose bisphosphate carboxylase/oxygenase (RuBisCO), emphasizing the change in structures during the catalytic cycle and during regulation [Eisenberg]. (4) Protein design of aggregates of small peptides, followed by x-ray and NMR studies of their structures in the crystalline and solution states [Eisenberg, Feigon]. Redesign of the lac permease protein, to render it soluble and crystallizable [Eisenberg]. The long range goal of this effort is to learn and confirm rules of protein folding. (5) Correlation of protein sequences with their three-dimensional structures by means of 3D Structural Profiles. Computational studies of protein stability and antigenicity [Eisenberg, Yeates]. (6) Determination of the crystal structure of the oxygen-evolving enhancer protein 1 (OEEI), with an emphasis on understanding its interaction with the catalytic manganese cluster and with the photosynthetic reaction center. Prediction of residues important in photolysis and electron transfer [Yeates]. (7) Development of two new procedures for macromolecular crystal structure determination [Yeates]. (8) Maintenance and upgrading of the communal x-ray data collecting facility. (9) Maintenance and upgrading of the communal computer graphics facility used by all investigators. (10) Upgrading of the macromolecular NMR facility, built around a 500 MH NMR spectrometer.